The rotational speed at which the rotor of a wind energy installation rotates is a safety-relevant parameter. If the rotational speed moves out of the intended rotational speed range, the wind energy installation may be damaged. The controller for the wind energy installation is set up such that the relevant rotational speed limits are not exceeded during normal operation. However, if faults occur in the wind energy installation, for example a defect in the controller or a faulty signal from a sensor, the situation may occur in which the wind energy installation no longer operates as intended and the rotational speed limits are exceeded.
An additional safety mechanism is provided for this situation. The rotational speed is continuously monitored using a rotational speed relay and a switch-off command is generated if a rotational speed limit value is exceeded. The switch-off command which has priority over the normal controller commands causes the wind energy installation to be deactivated as quickly as possible.
The rotational speed relay is checked for proper operation at regular maintenance intervals. Hitherto, the following method has been provided for this purpose. A service engineer travels to the wind energy installation and stops the latter. The rotational speed relay is reprogrammed to a new rotational speed limit value which can be exceeded during normal operation. The service engineer then starts the wind energy installation, with the result that the lower rotational speed limit value which has now been newly set is exceeded. The service engineer tests whether the rotational speed relay provides a switch-off command in the proper manner. If the test is positive, the wind energy installation is stopped again, the rotational speed relay is programmed back to the original rotational speed limit value and the wind energy installation is changed to normal operation again. This process is prone to errors. It is conceivable, inter alia, for the rotational speed relay to be programmed to an incorrect limit value, rather than the original limit value, at the end.